NITROGEN METABOLISM IN WHITE POTATO TUBER TISSUE INFECTED WITH FUNGI. CHANGES IN THE ALCOHOL-SOLUBLE AND -INSOLUBLE NITROGEN FRACTIONS

An increase of the ratio insoluble N/soluble N in potato tubertissue (var. Bintje) infected with Gibberella saubinetii orCerato-cystis fimbriata and incubated at 25° could onlybe demonstrated in samples cut from the area invaded by thefungi. In the non-infected controls some increase was foundin tissue close to the cut surface due to wound-reaction. The fungi hardly penetrated tuber tissue of var. Koopmans Blauwe,while tubers of var. Alpha were rather susceptible. Tissue ofvar. Bintje turned out to be rather resistant. Incubation at30° or 33° resulted in a more limited penetration bythe fungi. No relation exists between the value of the ratioinsoluble N/soluble N or the protein content of the host tissue,and the grade of resistance to the infection. Again, an increaseof insoluble N could only be observed in mycelium-containingsamples. The mycelia of both fungi had a ratio insoluble N/soluble Nwhich was much higher than the ratio of normal potato tissue.It was possible to explain the increase of the ratio in invadedtissue on the basis of the presence of hyphal substances. No evidence was obtained for a synthesis by the host tissueof insoluble nitrogenous compounds prior to, or concomitantwith, the increase of respiration rate after infection. To whatextent a wound-reaction played a role in the infected tuberparts is uncertain. The possibility of a simultaneous synthesisand breakdown of proteins after infection without a rise ininsoluble nitrogen is discussed. (Received February 3, 1966; )